I still think you have something causing the pistons to be pushed back in.

if you compare any other car with front disc, you shouldn't get any noticable movement of the calipers when you start to press the pedal down.

There is some minor retraction due to the o ring around the piston, but that is to take the drag off.

if you have enough movement to hear it something is wrong.

One of the old drag racer tricks was to loosen the nut holding the hub on so the disc rotor had some wobble and it would push the pistons back in as the car rolled giving less drag on the track.
hard on the bearings, but it seemed like the car would go faster.

I would ask you to see what kind of (I think the term is) run out your rotors have as you turn them.
see if they aren't pushing the pistons back in.